Chemoselective Proteomics, Zinc Fingers, and a Zinc(II) Model for H₂S Mediated Persulfidation

Abstract

The gasotransmitter hydrogen sulfide (H2S) is thought to be involved in the post‐translational modification of cysteine residues to produce reactive persulfides. A persulfide‐specific chemoselective proteomics approach with mammalian cells has identified a broad range of zinc finger (ZF) proteins as targets of persulfidation. Parallel studies with isolated ZFs show that persulfidation is mediated by ZnII, O2, and H2S, with intermediates involving oxygen‐ and sulfur‐based radicals detected by mass spectrometry and optical spectroscopies. A small molecule ZnII complex exhibits analogous reactivity with H2S and O2, giving a persulfidated product. These data show that ZnII is not just a biological structural element, but also plays a critical role in mediating H2S‐dependent persulfidation. ZF persulfidation appears to be a general post‐translational modification and a possible conduit for H2S signaling. This work has implications for our understanding of H2S‐mediated signaling and the regulation of ZFs in cellular physiology and development.

Synthesis, Characterization, and Reactivity of a Synthetic End-On Cobalt(II) Alkyl Persulfide Complex as a Model Platform for Thiolate Persulfidation

“…13 Most notably, iron−sulfur (Fe−S) cluster construction by the scaffold protein ISCU involves transfer of cysteine persulfides ( Cys SS − ) from cysteine desulfurase (IscS), and the exact mechanism of RSS − reduction to S 2− and eventual [2Fe−2S] cluster formation remains an active area of study. 14−16 Furthermore, persulfidation from cysteine thiolates mediated by both redox-active and redox-inactive metal centers has been observed in tetraprolin (TPP), 17,18 ZnCu superoxide dismutase, 19,20 cysteine dioxygenase, 21 NiFe hydrogenases, 22,23 and other iron−sulfur (Fe−S) cofactors during assembly/disassembly. 24−26 Sulfide detoxification is of paramount importance in mammals and is mainly achieved by ).…”

“…Regulation of biological H 2 S levels in most organisms involves the intermediacy of persulfides (RSS – ), which are typically in the form of translationally or post-translationally modified cysteine/glutathione residues bearing an additional sulfur atom in the −1 oxidation state. − RSS – are often reductant-labile sources of biological S 2– and have been widely implicated in mammalian H 2 S biogenesis by 3-mercaptopyruvatesulfurtransferase (3-MST) and also in the biosynthesis of essential S-containing cofactors including thiamin and molybdopterin. − Moreover, RSS – production, utilization, and regulation are often intertwined with bioinorganic metal centers (Figure ). Most notably, iron–sulfur (Fe–S) cluster construction by the scaffold protein ISCU involves transfer of cysteine persulfides ( Cys SS – ) from cysteine desulfurase (IscS), and the exact mechanism of RSS – reduction to S 2– and eventual [2Fe–2S] cluster formation remains an active area of study. − Furthermore, persulfidation from cysteine thiolates mediated by both redox-active and redox-inactive metal centers has been observed in tetraprolin (TPP), , ZnCu superoxide dismutase, , cysteine dioxygenase, NiFe hydrogenases, , and other iron–sulfur (Fe–S) cofactors during assembly/disassembly. − Sulfide detoxification is of paramount importance in mammals and is mainly achieved by persulfide dioxygenase (ETHE1), which is a nonheme iron-dependent oxygenase that catalyzes oxygenation of glutathione persulfide (GSS – ) to sulfite (SO 3 2– ). − The proposed mechanism involves initial end-on binding of GSS – to the mononuclear Fe II site, although the crystal structure of substrate-bound ETHE1 remains elusive due to the poor stability of persulfide-bound species . Furthermore, interactions of RSS – with metalloenzymes have also been observed in numerous sulfur-oxidizing bacteria and archaea that utilize Mo, heme, , and nonheme Fe , containing enzymes to catalyze the oxygenation of RSS – to SO 3 2– to provide additional electrons for carbon fixation and respiration.…”